Phylum: Charophyta   Family: Desmidiaceae

Staurastrum punctulatum L.A. de Brébisson ex J. Ralfs 1848

First described by Brébisson in Ralfs (1848: 133, pl. 22: 1) and illustrated by Jenner. A polymorphic species that occurs in tri-and quadri-radiate forms. In apical view they are straight-sided.
Cell dimensions: L: 26-40 µm, B: 23-36 µm, Is: 8-12 µm.
Widespread throughout Europe but not common in the Outer Hebrides. Found in moorland bogs and pools with variable acidity.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Ralfs, J. (1848) The British Desmidieae.
West, W. & West, G.S. (1912) A Monograph of the British Desmidiaceae, Volume 4.